Summary

This study describes for the first time the ultrastructure of moulting in a copepod. The moulting sequence in the chalimus II larva of L. salmonis corresponds well to that of other crustacea described to date. In common with euphausids, no period of reduced activity was observed in the epidermis suggesting either that a defined intermoult is absent or that it is of very short duration. It is hoped that this description will provide a baseline for studies of the control of moulting in sea lice and of the effects of exogenous compounds on moulting.